Atomic layer deposition (ALD) and chemical vapor deposition (CVD) are two common methods used in semiconductor fabrication to deposit thin films on a substrate. The processes deliver gases to a process chamber and onto a substrate where the gases react and form a thin film on the substrate. In some cases, deposition of a film on the edge or backside of the substrate is not desirable. Edge purge gas may be provided to prevent deposition at the edge of the substrate, often through channels in a substrate support member such as a support plate. Edge purge gas may help prevent backside deposition as well.
With some substrate supports, an edge region of a substrate rests upon a raised portion adjacent to the perimetrical edge of a support plate, with projections within the perimeter supporting interior portions of the substrate. A vacuum is often used to hold the substrate down to the substrate support, with the vacuum sometimes assisting in sealing the substrate against the raised portion of the support plate to lessen infiltration of process gasses to the backside of the substrate.
It is often desirable to supply the edge purge gas and vacuum through channels formed within the substrate support plate. Edge purge gas and vacuum supply channels in typical substrate supports are prone to inconsistent or unpredictable flow characteristics. Further, edge purge gas and vacuum supply channels in typical substrate supports can experience fluid leaks in operation, contributing to inconsistent or unpredictable flow characteristics of the channels.
Vacuum formation and purge gas flow are some of the considerations in determining processing parameters. Accordingly, the provision of an adequate and predictable vacuum and flow of edge purge gas are generally necessary to establish desirable processing parameters. It is generally desirable to maintain the fluid tight nature of these channels at least to maintain repeatable processes. It is also often desirable to keep the edge purge gas free of contamination, which may come from materials used to form the plate. Easily establishing and maintaining the integrity of the channels and any fluid tight seals between, for example, between the plate and the support shaft having integrated vacuum and edge purge lines, has presented difficulty in some substrate supports.
Current support plates typically require difficult and time consuming manufacturing operations to create channels capable of providing adequate and predictable edge purge gas and vacuum to the desired regions of the support plate.
Therefore, a need exists for a substrate support with easily formed edge purge gas and vacuum channels to provide adequate and predictable edge purge gas and vacuum to the support plate. A need also exists for a substrate support with edge purge gas and vacuum channels that can be maintained in a contaminant-free and fluid-tight condition while in operation.